1. Field of the Invention
The present invention relates to a system and a method for measuring electromagnetic waves, and a recording medium in which electromagnetic wave measurement control program is recorded. More particularly, the invention relates to measurement of electromagnetic waves emitted from an electronic device, which uses at least one electronic circuit, as electromagnetic interference.
2. Description of the Related Art
An apparatus or device including at least one electronic circuit (hereinafter called the electronic device) leaks electromagnetic waves out of the electronic device. The leaked electromagnetic waves would be electromagnetic interference causing malfunction and trouble in its peripheral devices. Consequently, electronic devices now put on the market are bound to suffice a gauge with respect to EMI (electromagnetic interference), which gauge is regulated by the Voluntary Control Council for Information Technology Equipment (VCCI).
For this purpose, electronic device manufacturers generally measure EMI of a model of the object electronic device at first, and then improve the electronic device in design based on the result of the EMI measurement on the model. The term xe2x80x9cmodelxe2x80x9d of the electronic device means an aggregation of models of one or more electronic circuits and a cabinet; the electronic circuits unitedly serve to perform operations of the electronic device and emit electromagnetic waves; while the cabinet accommodates and protects the electronic circuits and prohibits the leak of electromagnetic waves out of the electronic device.
Generally, the EMI measurement is performed using an EMI measurement system 100 shown in FIG. 8. In practice, a model (a measurement object) of an electronic device is disposed on a turntable 111, which angularly moves or rotates through 360 degrees about a vertical axis, in an anechoic chamber 101. A measuring antenna 112 measures (receives) electromagnetic waves emitted by (leaked from) the measurement object 113. And a spectrum analyzer 123 in a measurement room 102 analyzes electric field intensities, which correspond to respective frequencies, of the electromagnetic waves received by the measuring antenna 112.
The distance between the measurement object 113 and the measuring antenna 112 is approximately 3 meters or 10 meters as regulated in accordance with the gauge. The spectrum analyzer 123 is connected to a control personal computer (hereinafter also called the control PC) 124 by a general purpose interface bus (GPIB). The result of analysis by the spectrum analyzer 123 is sent to the control PC 124 as EMI measurement result data, and the control PC 124 stores the result in a storage unit 125, such as a hard disk.
The measurement object 113 emits electromagnetic waves in all directions. It is enough that the highest electric field intensity of the electromagnetic waves emitted from the measurement object 113 is lower than an intensity regulated by VCCI as an EMI gauge (hereinafter called the VCCI gauge). For this purpose, it is necessary to identify a point where the electromagnetic wave corresponding to the highest intensity is received. To identify the point, the electric field intensity of the received electromagnetic wave is measured under a measurement condition, which is changed by angularly moving or rotating the turntable 111 to change the orientation or posture of the measurement object 113 within the horizontal plane and also to change the height of the measuring antenna 112 within the range from 1 meter to 4 meters.
Although the measurement condition changing in, e.g., the angle of rotation of the turntable 111 or the height of the measurement antenna 112, may be manually performed, the control PC 124 disposed in the measurement room 102 automatically controls a turntable rotation motor 111a and an antenna height control motor 112a using a turntable controller 121 and an antenna height controller 122, which are connected to the control PC 124 by GPIB or the like.
In the conventional EMI measurement, the measuring antenna 112 receives electromagnetic waves under the various measurement conditions in which the angle of rotation of the turntable 111 and the height of the measuring antenna 112 are changed, thereby measuring the electromagnetic waves (emitted from the measurement object 113) with respect to all directions. Finally, it is discriminated whether or not the highest electric field intensity meets the VCCI gauge.
The intensity of the electromagnetic waves emitted from the measurement object 113 highly depends on not only the electromagnetic waves emitted from individual electronic circuits but also the electromagnetic shield characteristic of the cabinet accommodating the electronic circuits. When the cabinet has a superior electromagnetic shield characteristic, it is possible for the measurement object 113 to meet the VCCI gauge despite of a relatively high electric field intensity of the electromagnetic waves emitted by the electronic circuits. Therefore, if it is impossible for the electronic circuits to reduce generation of the electromagnetic wave any more, the electromagnetic shield of the cabinet is reinforced so that the electromagnetic waves emitted from the measurement object 113 would meet the VCCI gauge as a whole.
As mentioned above, since the electromagnetic shield characteristic of the cabinet is highly regarded satisfaction with the VCCI gauge, there have been proposed systems for measuring (evaluating) the cabinet module in terms of the electromagnetic shield characteristic. Such measurement system is exemplified by Japanese Patent Laid-Open Publication No. HEI 6-43197 (see a measurement system 200 as shown in FIG. 9 of the accompanying drawings).
The measurement system 200 of FIG. 9 performs EMI measurement as follows:
First of all, a transmitting antenna (spheric dipole antenna) 214, which is supposed to be an electronic circuit that emits electromagnetic waves, is accommodated in the cabinet 213 in an experimental site 201, such as an anechoic chamber. An oscillator (signal generator) 221 in a measurement room 202 is driven so as to produce an electric signal causing the transmitting antenna 214 to emit electromagnetic waves. Then, the electric signal is converted into an optical signal by an electric/optical (E/O) converter 222, whereupon the optical signal is introduced to the transmitting antenna 214 via a sending optical fiber cable 203.
The transmitting antenna 214 is in the form of a spheric conductor having such a size as to be accommodated in the cabinet 213 (e.g., 15 cm in diameter). A non-illustrated optical/electric (O/E) converter and a battery or the like are incorporated in the transmitting antenna 214. The O/E converter in the transmitting antenna 214 converts an optical signal, which has been received through the optical fiber cable 203, into an electric signal in the form of electromagnetic waves, which are emitted uniformly in all directions over the experimental site 201.
Electromagnetic waves leaked from the cabinet 213 are received by a measuring antenna (receiver spheric dipole antenna) 212, and are converted into an optical signal by a non-illustrated E/O converter incorporated in the measuring antenna 212. The optical signal is input to an O/E converter 223 in the measurement room 202 via a receiving optical fiber cable 204. The O/E converter 223 then converts back to an electric signal. Finally, the electric signal is received by the receiver 224, such as a spectrum analyzer.
Since the electromagnetic wave leaked from the cabinet 213 is measured by the above-mentioned manner, it is possible to examine and evaluate the electromagnetic shield characteristic of the cabinet 213.
The optical fiber cables 203, 204 serve to connect the oscillator 221 and transmitting antenna 214, the measuring antenna 212 and the receiver 224 so as to eliminate possible influence on the result of EMI measurement in the EMI measurement system 200. Namely, if an electrical cable, e.g. a coaxial cable substituting for the optical fiber cables 203, 204, the result of EMI measurement would be affected by the electromagnetic waves leaked from the electrical cable.
If the measurement object has a plurality of electronic circuit blocks accommodated in the cabinet 213, the all electronic circuit blocks and the cabinet have to be collected in the anechoic chamber 201 to perform EMI measurement in the EMI measurement system 100 of FIG. 8. But if the measurement object is a large-scale electronic device, such as an exchange, it is very difficult to dispose the measurement object on the turntable 111 and to perform the EMI measurement under the same condition as an actual installation environment.
In the conventional method, therefore, since efforts to reduce or eliminate EMI are made on many occasions after installation of an electronic device, the electronic device installation and EMI countermeasure would be expensive and time-consuming.
As a solution, the spheric dipole antenna of FIG. 9 is used as an electromagnetic wave source that emits electromagnetic waves resembling those of the electronic device, as disclosed in Japanese Patent Laid-Open Publication NO. HEI 5-333072. Measurements are performed on electromagnetic wave propagation characteristics both in the actual installation place and in the experimental site (e.g., the anechoic chamber 101) and on the electromagnetic wave emitted in the experimental site. And the distribution of EMI is estimated when the electronic device is installed in the actual installation place based on the result of the measurement.
In this prior art, since the EMI of an electronic device is estimated before the installation, it is possible to take a countermeasure against EMI in advance.
A manufacturing process (product development process) of an electronic device is assumed. The manufacturing process includes EMI measurement. Assumed that the manufacturing process is performed on a large-scale electronic device, such as an exchange, since an exchange accommodates a plurality of electronic circuit blocks and a complex cabinet, the respective parts tend to be developed in separated place and at separated time, as shown in FIG. 10.
More specifically, a cabinet model is manufactured in a cabinet design process 300 (Steps A1, A2), and the individual electronic circuit block models are manufactured in the respective circuit design processes 400 (Steps B1, B2) irrespective of the cabinet design process 300.
When the EMI measurement is performed on the model 113 in the EMI measurement system 100, the cabinet and the electronic circuit blocks, which are independently designed in the processes 300, 400, are collected in the anechoic camber 101 at the same time, and the model 113 is assembled using the cabinet and the electronic circuit blocks. Finally, the EMI measurement is performed on the model 113 (Steps C1, C2).
On the basis of the result of the EMI measurement, a countermeasure is taken on the cabinet and/or the electronic circuit blocks to meet the VCCI gauge: a cabinet product is designed (Step A3) in cabinet design process 300; and the debug operations to the model hardware and software, which operations are original purposes for the models, are performed on the respective electronic circuit blocks (Step B3); and the electronic circuit block products are designed (Step B4) in the respective circuit design process 400.
Upon the completion of the individual products (Steps A4, B5), the cabinet product and the all electronic circuit block products are collected again in the anechoic chamber 101 and are assembled (Step C3). Finally, EMI measurement is performed on the electronic device, which is going to be put on the market, as a whole (Step C4).
As a result, the cabinet and the electronic circuit blocks need to be collected in the anechoic chamber 101 in the conventional EMI measurement system 100 each time when EMI measurement is carried out. In particular, when EMI measurement is performed on a large-scale electronic device, such as an exchange, the EMI measurement causes a considerable load on the entire development process.
The electronic circuit block models are manufactured not only for EMI measurement but also mainly for the debug operations with respect to its hardware and software. But, as described above, the debug operations halt during EMI measurement (hatched part in FIG. 10).
Further, when the electronic device includes a plurality of electronic circuit blocks, as the above-mentioned example, and one of the electronic circuit blocks is modified in specification after the EMI measurement, the cabinet and the all electronic circuit blocks including, of course, unmodified electronic circuit blocks are re-collected, re-assembled, and re-performed the EMI measurement. In this case, the debug operations with respect to the unmodified electronic circuit blocks are also interrupted.
In particular, when manufacturing plants are decentralized in separated places for labor division, plural electronic circuit blocks unitedly constitute an electronic device are usually designed and developed in respective different places. In that case, it is very inefficient to collect all the electronic circuit blocks at a measurement site each time when EMI measurement is performed.
Upon EMI measurement, if electromagnetic waves resembling those of respective electronic circuit block is emitted in the anechoic chamber 101, so that it is possible to avoid such unreasonable operation. As a solution, it would be possible to realize electromagnetic waves emission resembling those of the electronic circuit blocks by using technique disclosed in Japanese Patent Laid-Open Publications No. HEI 5-333072 and No. HEI 6-43197.
These publications disclose a concept of xe2x80x9celectromagnetic wave emission characteristic resembling those of an electronic device is emitted,xe2x80x9d however the concept simply reveals that a spheric dipole antenna is supposed to be an electromagnetic wave emitting source (electronic circuit). Additionally, the publications do not disclose or suggest a method or means for emitting electromagnetic waves exactly resembling those of an electronic device (electronic circuit block) in combination or respectively.
In particular, Japanese Patent Laid-Open Publication No. HEI 5-333072 discloses that xe2x80x9cit is impossible for an emitting source to emit electromagnetic waves exactly resembling those of an electronic devicexe2x80x9d in the paragraph of [0007]. Further, since either one of the two publications does not aim to xe2x80x9cemit electromagnetic waves exactly resembling those of an electronic device,xe2x80x9d it is obvious that the two publications fail to mention the method for exactly emitting electromagnetic waves resembling those of an electronic device.
In conclusion, even if the EMI measurement system 100 of FIG. 8 simply combines with the technique disclosed in the above-mentioned Japanese Patent Publications, it is impossible to emit electromagnetic waves resembling those of respective electronic circuits and to perform EMI measurement on an electronic device consists the electronic circuits without gathering the electronic circuits in the anechoic chamber 101.
With the foregoing problems in view, it is an object of the present invention to provide a system and a method for emitting electromagnetic waves exactly resembling those of an electronic circuit, which is an element of an electronic device.
Another object of the present invention is to provide a recording medium in which electromagnetic wave measurement control program is recorded for emitting electromagnetic waves exactly resembling those of an electronic circuit.
With the system, the method, and the recording medium, it is possible to perform electromagnetic wave measurement as if all electronic circuits constitute an electronic device are gathered, when the circuits are not collected.
To attain the first-named object, according to a first generic feature of the present invention, there is provided a system for measuring electromagnetic waves of an object electronic circuit, comprising: an electromagnetic wave emitting unit for emitting electromagnetic waves; an electromagnetic wave receiving unit, disposed relatively near to the electromagnetic wave emitting unit, for receiving the electromagnetic waves emitted by the electromagnetic wave emitting unit; measurement condition changing means for changing an electromagnetic wave measurement condition between the electromagnetic wave emitting unit and the electromagnetic wave receiving unit; an electromagnetic wave measuring unit, operatively connected with the electromagnetic wave receiving unit, for measuring the electromagnetic waves received by the electromagnetic wave receiving unit; and a control unit, operatively connected with the electromagnetic wave emitting unit and the measurement condition changing means, for controlling the electromagnetic wave emitting unit and the measurement condition changing means based on actual measurement data of the object electronic circuit, which data has previously been measured under a predetermined measurement condition, and measurement condition data of the predetermined measurement condition in such a manner that electromagnetic waves resembling those of the object electronic circuit is emitted from the electromagnetic wave emitting unit under the same condition as the predetermined measurement condition.
In the electromagnetic wave measuring system (hereinafter also called xe2x80x9cmeasuring systemxe2x80x9d), obtaining the actual measurement data of the object electronic circuit, which data has previously been measured under a predetermined measurement condition, and the measurement condition data of the predetermined measurement condition (data obtaining step), the control unit controls the electromagnetic wave emitting unit and the measurement condition changing means based on the actual measurement data of the object electronic circuit and the measurement condition data of the predetermined measurement condition in such a manner that electromagnetic waves resembling those of the object electronic circuit is emitted from the electromagnetic wave emitting unit under the same condition as the predetermined measurement condition (controlling step), and measures the electromagnetic waves received by the electromagnetic wave receiving unit (measuring step).
As a result, since it is possible for the emitting unit to emit electromagnetic waves exactly resembling those of the object electronic circuit, the electromagnetic waves emitted from the electronic device can be measured using the resembling electromagnetic waves as substitution for electromagnetic waves actually emitted by the object electronic circuit even when the object electronic circuit is not at the measuring site.
Namely, since the control unit controls the current measurement condition and the electromagnetic wave emitting unit in electromagnetic wave emission state based on the actual measurement condition and the corresponding measurement condition data of the object electronic circuit in such a manner that the emitting unit emits electromagnetic waves exactly resembling those of the object electronic circuit, the electromagnetic waves emitted from the electronic device can be measured using the resembling electromagnetic waves as substitution for electromagnetic waves actually emitted by the object electronic circuit even when the object electronic circuit is not at the measuring site. Further, since it is possible to measure the electromagnetic waves emitted from the electronic device as if all the electronic circuits constitute the object electronic device are gathered at the same time even when the all electronic circuits are not gathered, it is possible to extremely improve the efficiency in the development process of the individual electronic circuits free from the development process of other electronic circuits.
To attain the second-named object, according to the third generic feature of the present invention, there is provided a recording medium in which an electromagnetic wave measurement control program for instructing a computer to execute processes including the data obtaining step and the controlling step. A computer reads the electromagnetic wave measurement control program and executes in accordance with the control program so as to control the electromagnetic wave measurement system and complete the electromagnetic wave measurement.
As a preferable feature of the present invention, the electromagnetic wave measurement control program may further instructs the computer to execute the steps of (b1) controlling the measurement condition changing means and the electromagnetic wave emitting unit in electromagnetic wave emission state in accordance with the measurement condition data and the actual measurement data so as to obtain electromagnetic-wave-emission-state data of the electromagnetic wave emitting unit when current measurement data of the electromagnetic waves received by the electromagnetic wave receiving unit coincides with the actual measurement data; and (b2) controlling the electromagnetic wave emitting unit in electromagnetic wave emission state in accordance with the electromagnetic-wave-emission-state data so as to render the electromagnetic wave emitting unit to emit intended electromagnetic waves resembling those of the object electronic circuit.
With these processes, the emitting unit emits electronic waves exactly resembling those of the object electronic circuit as if the object electronic circuit actually emits the electromagnetic waves.
Since the emitting unit in electromagnetic wave emission state is controlled in accordance with the electromagnetic-wave-emission-state data compensated in such a manner that the current measurement data of the electromagnetic waves received by the electromagnetic wave receiving unit coincides with the actual measurement data, it is further possible to emit electromagnetic waves exactly resembling those of the object electronic circuit with high accuracy.
As another preferable feature, the electromagnetic-wave-emission-state data, which has been obtained in the controlling step (b1), may be recorded in a storage unit. If an electronic circuit is changed in specification, the electromagnetic-wave-emission-state data with respect to other electronic circuits can be used as substitution for electromagnetic waves actually emitted from the respective electronic circuit as long as the specification, the measurement condition data, and the actual measurement data of the electronic circuit module are free from modification or changing.
Further, when the electromagnetic-wave-emission-state data is recorded in the storage unit, the electromagnetic-wave-emission-state data with respect to a modified-free electronic circuit can be reused. Namely, the electromagnetic-wave-emission-state data with respect to electronic circuits can be used as substitution for electromagnetic waves actually emitted from the respective electronic circuit as long as the specification, the measurement condition data, and the actual measurement data of the electronic circuit module are free from modification or changing. With the electromagnetic-wave-emission-state data stored in the storage unit, since, when the electromagnetic wave measurement is re-performed on a combination of a modified electronic circuit and modified-free electronic circuits, it is possible to perform the EMI measurement of the combination in the absence of the modified-free electronic circuit modules in the measurement site, it is possible to carry out respective development processed without affected by those of other electronic circuits.
As still another preferable feature, if said actual measurement data has been obtained over a frequency domain, the controlling step (b1) may includes the steps of performing an inverse Fourier transformation on said actual measurement data to obtain oscillated waveform data over a time domain; and producing an oscillated waveform of the electromagnetic wave emitted from the electromagnetic wave emitting unit based on the oscillated waveform data obtained by the inverse Fourier transform performing step. With such transformation performing and controlling process, since it is possible to control the emitting unit in electromagnetic wave emission state with respect to a plurality of frequencies included in the frequency domain of the actual measurement data only by a single signal input, the measurement operation can be streamline and simplified.
As an additional preferable feature, if there are provided a plurality of sets of the measurement condition data and the actual measurement data in accordance with a plurality of different measurement conditions, the control unit may control the measurement condition changing means and the electromagnetic wave emitting unit in electromagnetic wave emission state for the individual sets one after another in a predetermined sequence. With this manner, it is possible to emit electromagnetic waves resembling those of electronic circuit under plural measurement conditions with higher accuracy.
As still another preferable feature, if there are provided a plurality of sets of the measurement condition data and the actual measurement data, the control unit may further include data sorting means for sorting the plural sets of the measurement condition data and said actual measurement data into an order suitable for the measurement condition changing. With the data sorting means, since the electromagnetic wave measurement is performed in the most effective order, it is possible to further streamline and simplify the measurement operation.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.